Study On The Influence Of Pitch System On Wind Turbine Operating Performance

Wind power generation is the most commercialized and potential renewable energy technology at present.The mainstream commercial wind turbines adopt variable-speed,variable blade-pitch-to –feather configuration.As a key subsystem,the pitching system shoulders important responsibilities such as load control,power regulation and aerodynamic braking,which is of great importance to the safe operation of wind turbines.The study of the influence of the pitching system on the dynamic characteristics,is of great significance to the design of the key components and the shutdown strategy,the improvement of the reliability and the reduction the cost of operation and maintenance.(1)The double-fed offshore wind turbine is studied,this paper introduces the AeroServo-Elastic coupling simulation process in SIMPACK,gives the flexible body modeling parameters and methods,such as blade and tower,finally,the Aero-ServoElastic coupling dynamic model with detailed drivetrain is developed,which provide the supports to the study of the influence of the pitching system on the dynamic characteristics on next step.(2)The influence of the pitching system response speed and steady accuracy on the dynamic characteristics of the wind turbine is studied,based on the coupling dynamic model.The results show that: The slower the response speed of the pitching system is,the longer the time it takes to adjust the generator power and speed when the wind speed has a big change(such as gust).In the process of adjustment,the faster the response speed is,the larger the minimum value of generator power and rotation speed will be,and the smaller the minimum value of Y-axis bending moment(My)around the tower bottom will be,or even the reverse situation will occur.(3)The dynamic characteristics of wind turbine is studied when the steady error of blade occurs,the standard deviation of bending moment of main-shaft bearing and tower bottom is several times the normal operation,and increases with the increase of the steady error absolute value.When the steady error increases(from negative to positive),the load performance of the first planetary gear meshing force distributed along the tooth width becomes worse,and the load at the downwind increases.(4)When the pitch system is stuck,the bending moment of tower bottom around X,Z axis and main-shaft bearing A around Y and Z axis fluctuates greatly,which standard deviation is several or even ten times of that under normal operating conditions.The load sharing coefficient of the first planetary gear increases.Meanwhile,the distribution of the first planetary gear load along the tooth width goes bad,the upwind load increases.With the increase of the average wind speed,each bending moment standard deviation ratio of blade stuck condition to normal operation condition increases first and then decreases.(5)The dynamic characteristic of wind turbine under emergency shutdown due to pitch system stuck is studied,the results show that: The bending moment of the tower bottom around the Y-axis,the pitching moment of the main-shaft,the vibration acceleration and displacement in the x-direction(front and back)of the nacelle,and the displacement in the y-direction of the nacelle are greater than the normal shutdown.The main frequency component is 0.24 Hz,corresponding to the first order of yaw oscillation natural frequency.